1. Field of the Invention
The present invention relates to a transmitting system, a transmitting method and a transmitting/receiving system, and more particularly to those where commands for reading out audio level information are defined so that the audio level information of a controlled audio apparatus connected via an IEEE1394 bus can be read out therefrom by a control apparatus.
2. Description of the Related Art
Recently, there is proposed a system where data can be transferred between electronic apparatus such as an audio apparatus and a personal computer connected mutually via an IEEE (Institute of Electrical and Electronics Engineers) 1394 bus.
An IEEE1394 bus employed in such a system is a serial bus adapted for fast transfer of data similarly to an SCSI (Small Computer Systems Interface). The use of this bus enables transfer of both data and a control command via a single cable by two methods termed isochronous transfer and asynchronous transfer.
Consequently, it becomes possible to control, by means of a control apparatus such as a personal computer, a recording, reproduction or stop operation of any target apparatus to be controlled, such as an MD (Mini Disc) player or the like, or to control editing of tracks such as division, coupling or erasure thereof.
In this system, transfer of audio level information is rendered necessary to realize an application where, as in an audio level meter for example, its display is changed in accordance with the audio level of a predetermined audio signal recorded or reproduced in an audio apparatus. However, in the conventional system known heretofore, there exists a problem that audio level information cannot be acquired since any command for reading out the audio level information of an audio apparatus connected via an IEEE1394 bus is not defined.
It is therefore an object of the present invention to provide a transmitting system, a transmitting method and a transmitting/receiving system where an output level can be set in a controlled target apparatus from a control apparatus through connection via an IEEE1394 bus, and a command signal sent from the control apparatus to the target apparatus can be set for reading out the preset output level from the target apparatus by the control apparatus.
According to a first aspect of the present invention, there is provided a transmitting system where unitary data having an isochronous gap for transmission of main data and an asynchronous gap for transfer of command data are transmitted between a control apparatus and a controlled target apparatus via a predetermined bus. The control apparatus comprises a sending means for sending an identifier to identify the target apparatus by the use of the asynchronous gap, and also a command to request transfer of a signal level from the controlled target apparatus. And the target apparatus comprises a receiving means for receiving the target apparatus identifier transmitted by the use of the asynchronous gap from the sending means of the control apparatus via the predetermined bus, and also receiving the command to request transfer of a signal level from the target apparatus; and a sending means for sending the signal level in response to the signal-level transfer command received by the receiving means.
According to a second aspect of the present invention, there is provided a transmitting method whereby unitary data having an isochronous gap for transmission of main data and an asynchronous gap for transfer of command data are transmitted between a control apparatus and a controlled target apparatus via a predetermined bus. This method comprises a step of sending, from the control apparatus to the target apparatus, an identifier to identify the target apparatus by the use of the asynchronous gap, and also a command to request transfer of a signal level from the target apparatus; a step of receiving the target apparatus identifier transmitted by the use of the asynchronous gap via the predetermined bus, and also receiving the command to request transfer of a signal level from the target apparatus; and a step of sending the signal level from the target apparatus to the control apparatus in response to the received command which requests transfer of the signal level from the target apparatus.
And according to a third aspect of the present invention, there is provided a transmitting/receiving system for receiving unitary data having an isochronous gap and an asynchronous gap and transmitted from a control apparatus via a predetermined bus. This system comprises a receiving means for receiving a target apparatus identifier transmitted from the control apparatus via the predetermined bus by the use of the asynchronous gap, and also receiving a command to request transfer of a signal level from the target apparatus; and a sending means for sending the signal level in response to the signal-level transfer request command received by the receiving means.
The above and other features and advantages of the present invention will become apparent from the following description which will be given with reference to the illustrative accompanying drawings.